Temperature dependence of magnetic hysteresis

Hysteresis measurements have become a routine procedure in characterizing the magnetic remanence carriers of rocks. In this study we have investigated the temperature dependence of magnetic hysteresis in order to better recognize the dominant anisotropy and changes of domain state at various temperatures. Hysteresis properties have been measured at a series of temperatures between 20 K and 873 K for synthetic magnetites and natural (titano)magnetite-bearing samples. For synthetic samples and gabbros, shape anisotropy dominates most temperature ranges, while magnetocrystalline anisotropy controls hysteresis properties below 120 K. Titanomagnetite-bearing oceanic basalts show quite different behavior with much higher coercivity, resulting from prominent magnetostrictive anisotropy. While many factors such as composition, field treatment, grain shape and size, and stress affect hysteresis properties at various temperature ranges, a dominant anisotropy was better recognized when remanence ratio was plotted against coercivity.